Optical decoding optical readers digitize image data prior to subjecting the image data to decoding processing such as bar code symbology decoding or OCR decoding. It is generally known that the best digitizing algorithm for use in digitizing a certain set of image data depends on features of the image data. A digitization method that may be useful for digitizing image data under a first imaging condition or which correspond to a first type of symbol may not be useful for digitizing image data captured under a second set of imaging conditions or which corresponds to a second type of symbol.
The approach of prior artisans who are cognizant of the fact that a best digitization method for a particular set of image data may vary depending upon features of the image data has been to successively subject the set of image data to multiple digitization algorithms. U.S. Pat. No. 6,082,621, for example, describes an analog digitizer for developing a series of “1” value or “0” value pixel values wherein an analog signal is subjected to multiple grey-to-binary conversion threshold values. If decoding the image data digitized utilizing the first binary conversion threshold fails, the image data is redigitized using a second binary conversion threshold and subjected to decoding again. If decoding again fails, the image data is digitized again using a third binary conversion threshold and so on. In digitization methods which use the reiterative decoding attempt approach method, the digitizing methods useful for digitizing the most commonly encountered image features are tried first, and the least commonly encountered image features last.
It can be seen, therefore, that the above approach can be extremely time consuming. For decoding image data having image features that can be digitized using a method for digitizing rarely seen image features, the image data is subjected to multiple digitation methods and decoding attempts before one is successful. Furthermore, if a symbol representation of a set of image data is of a type that cannot be decoded, several attempts to digitize and decode the symbol representation are nevertheless made.